International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
(Leptochloa panicoides)

Inhibition of Acetyl CoA Carboxylase HRAC Group 1 (Legacy A)

United States, Louisiana
Amazon Sprangletop (Leptochloa panicoides) is a monocot weed in the Poaceae family.  In Louisiana this weed first evolved resistance to Group 1 (Legacy A) herbicides in 2009 and infests Rice.   Group 1 (Legacy A) herbicides are known as Inhibition of Acetyl CoA Carboxylase (Inhibition of Acetyl CoA Carboxylase ).  Research has shown that these particular biotypes are resistant to cyhalofop-butyl, and fenoxaprop-ethyl and they may be cross-resistant to other Group 1 (Legacy A) herbicides.

The 'Group' letters/numbers that you see throughout this web site refer to the classification of herbicides by their site of action. To see a full list of herbicides and HRAC herbicide classifications click here.

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QUIK STATS (last updated Aug 09, 2011 )

Common NameAmazon Sprangletop
SpeciesLeptochloa panicoides
GroupInhibition of Acetyl CoA Carboxylase HRAC Group 1 (Legacy A)
Herbicidescyhalofop-butyl, and fenoxaprop-ethyl
LocationUnited States, Louisiana
Contributors - (Alphabetically)Jason Norsworthy 
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Confirmation Tests

Greenhouse trials comparing a known susceptible Amazon Sprangletop biotype with this Amazon Sprangletop biotype have been used to confirm resistance. For further information on the tests conducted please contact the local weed scientists that provided this information.

Genetic studies on HRAC Group 1 resistant Amazon Sprangletop have not been reported to the site.  There may be a note below or an article discussing the genetics of this biotype in the Fact Sheets and Other Literature
Mechanism of Resistance

The mechanism of resistance for this biotype is either unknown or has not been entered in the database.  If you know anything about the mechanism of resistance for this biotype then please update the database.
Relative Fitness

There is no record of differences in fitness or competitiveness of these resistant biotypes when compared to that of normal susceptible biotypes.  If you have any information pertaining to the fitness of Group 1 (Legacy A) resistant Amazon Sprangletop from Louisiana please update the database.
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University Of Arkansas
Department Of Crop
Soil, And Environmental Sciences
1366 West Altheimer Drive
Williams Hall
Fayetteville, 72704, Arkansas
United States
Email Jason Norsworthy
Web   : Web Site Link


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Louisiana have been instrumental in providing you this information. Particular thanks is given to Jason Norsworthy for providing detailed information.
Herbicide Resistant Amazon Sprangletop Globally
(Leptochloa panicoides)
Herbicide Resistant Amazon Sprangletop Globally
(Leptochloa panicoides)
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Herbicide Resistant Amazon Sprangletop Globally
(Leptochloa panicoides)
#CountryFirstYearSituationActive IngredientsSite of Action
1 United States (Louisiana) United StatesLouisiana2009 Rice cyhalofop-butyl, and fenoxaprop-ethyl 45 Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)
267Leptochloa panicoidesAmazon Sprangletop5565
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